Design of railway bridges considering LCA

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Design of railway bridges considering LCA

VINCENT THIEBAULT

Master of Science Thesis

Stockholm, Sweden 2010

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Design of railway bridges considering LCA

Vincent Thiebault

June 2010

TRITA-BKN. Master Thesis 305, 2010 ISSN 1103-4297

ISRN KTH/BKN/EX-305-SE

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Department of Civil and Architectural Engineering Division of Structural Design and Bridges

Stockholm, Sweden, 2010

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Preface

This Master Thesis was carried out at the Division of Structural Design and Bridges, at the Royal Institute of Technology (KTH) in Stockholm. The work was conducted under the supervision of Prof. Raid Karoumi to whom I want to thank for his advice, guidance, and for always having time for discussions. I also wish to thank Guangli Du for reviewing the manuscript of this report and providing valuable comments for improvement, and for always being available for help and discussions. I also thank Prof. Helge Brattebø and Johanne Hammervold for their advice and guidance within the framework of the ETSI project. I finally thank Ilkka Mansikkamäki for helping me to translate Finnish literature into English.

Finally, I would like to thank my parents, Hervé and Catherine, my siblings Romain, Claire and Peggy, and my friends for their understanding, support and encouragement.

Stockholm, June 2010

Vincent Thiebault

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Abstract

Environmental awareness has strongly increased these last years, especially in the developed countries where societies have become increasingly preoccupied by the natural resource depletion and environmental degradation. At the same time, the increasing mass transportation demand throughout the European Union requires the development of new infrastructures. Life Cycle Assessment is increasingly used to provide environmental information for decision-makers, when a choice is to be made about the transportation mode to be implemented on a given route. In a life-cycle perspective, not only the environmental pressure of the operation of vehicles but also the burden from the infrastructure, in particular bridges as key links of the road and railway networks, has to be assessed when comparing transportation modes.

Based on an extensive literature review, a simplified quantitative LCA is implemented in order to compare the environmental performance of two railway bridge designs. It is meant to be useful at an early stage in the design process, when no detailed information about the bridge is available, and when rough environmental estimations are needed. The Excel based model covers the entire life-cycle of the bridge, from raw material extraction to construction materials recycling and disposal. Various assumptions and omissions are made to narrow the scope of the analysis. For instance, processes that are found insignificant in the literature are omitted, and only a limited set of relevant emissions and impacts to the environment is considered. The model provides fully transparent results at the inventory and impact assessment level.

The streamlined approach is tested by comparing the environmental burden throughout the life-cycle of a steel-concrete composite railway bridge on a single span, equipped with either a ballasted or a fixed concrete single track. The results show that the environmental impacts of the fixed track alternative are lower than that of the ballasted track alternative, for every impact categories. In a sustainable development perspective, it would thus have been preferable to install a fixed track over the bridge to reduce its overall impact on the environment by about 77%. The raw material phase is found decisive in the life-cycle of both alternatives. The frequency of the replacement of the track is identified as a key environmental parameter, since the road traffic emissions during bridge closure nearly overwhelmed the other life-cycle stages.

Keywords: Life Cycle Assessment (LCA), streamlined approach, Railway bridges, ballasted track, fixed concrete track, steel-concrete composite bridges, Bothnia Line.

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Résumé

La sensibilisation à la protection de l’environnement a fortement augmenté ces dernières années, tout particulièrement dans les pays développés où les sociétés sont devenues de plus en plus préoccupées par la raréfaction des ressources naturelles et la dégradation de l’environnement. Dans le même temps, la croissance de la demande de transport de masse à travers l’Union Européenne requiert la construction de nouvelles infrastructures. L’Analyse du Cycle de Vie est de plus en plus utilisée pour fournir des informations aux décideurs, lorsqu’il faut choisir entre différents modes de transport sur un itinéraire donné. D’un point de vue global, l’impact environnemental des véhicules en circulation doit être évalué lorsque des modes de transport sont comparés, mais également l’empreinte environnementale des infrastructures, et en particulier des ponts, maillons clés des réseaux routiers et ferroviaires.

Basée sur une recherche documentaire approfondie, une Analyse du Cycle de Vie quantitative et simplifiée est implémentée afin de comparer les performances environnementales de deux ponts ferroviaires. Le model est utilisable tôt dans le processus de conception, au stade des avant-projets par exemple, lorsqu’aucune information détaillée concernant le pont n’est connue, et lorsque des estimations grossières quant aux performances environnementales sont nécessaires. Le model Excel couvre la totalité du cycle de vie du pont, de l’extraction des minerais jusqu’au recyclage des matériaux de construction. Des hypothèses ont été avancées pour réduire le champ de l’analyse. Par exemple, les processus jugés insignifiants dans la littérature ont été omis, et seul un nombre limité d’émissions et d’impact environnementaux a été considéré. Le model fournit des résultats parfaitement transparents tant au niveau de l’inventaire du cycle de vie que de l’évaluation des impacts.

Cette approche simplifiée est testée en comparant l’empreinte environnementale d’un pont composite acier-béton à une travée, sur la Ligne Grande Vitesse de Botnie en Suède, équipée d’une voie ballastée ou d’une voie sur dalle. Les résultats montrent que les impacts environnementaux de l’alternative sur dalle sont inférieurs à ceux de l’alternative ballastée, et ce pour toutes les catégories d’impacts. Dans une perspective de développement durable, il aurait donc été préférable d’installer une voie sur dalle sur le tablier du pont, de manière à réduire l’impact global sur l’environnement d’environ 77%. La phase d’extraction des minerais est primordiale dans le cycle de vie des deux alternatives. La fréquence de remplacement des voies a été identifiée comme étant un paramètre environnemental clé, puisque les émissions dues au trafic routier pendant la fermeture du pont pour maintenance submergent presque les autres phases du cycle de vie du pont.

Mots-clés: Analyse du Cycle de Vie (ACV), approche simplifiée, ponts ferroviaires, voie ballastée, voie sur dalle, ponts composites acier-béton.

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Chapter 1 Introduction

1.1 Background

1.1.1 Towards a European high-speed passenger network

It is difficult to think a sustainable economic growth without an efficient transport system, which links cities and activities together and allows flourishing exchanges between civilizations. Even if the 21^st century is announced as the advent of the information society and virtual trade, the need for travel is not expected to slow down.

However, the opposite is true.

The Transport White Paper, adopted in 2001 by the European Commission, described the situation regarding transport at that time, and put forward an action plan to meet the transportation demand by 2010 (European Commission, 2001). The figures mentioned in this section have been found in this document.

The European integration and economic growth will dramatically increase communication and exchange among people, leading to the emergence of new needs and an increased demand of 24% by 2010, in comparison with 2001, for passenger transport across the continent.

Concerning goods transport in the European Union, growth is due to a large extent to a shift from a “stock” economy to a “flow” economy for the last 20 years. Reduced production costs in Eastern Europe and the abolition of frontiers within the Union have led to a relocation of some industries, particularly for products that require high labor input. Production sites are nowadays commonly hundreds or thousands of kilometers away from the final customers: the demand for goods transportation is expected to be 38% higher in 2010 than 10 years earlier.

Europe started to suffer from congestion on several routes and areas during the 1990s, so that it is now threatening its economic competitiveness: traffic jams cost Europe 0.5% of the community gross domestic product (GDP) in 2001. Moreover, these traffic delays result in an extra consumption of 1.9 billion liters of fuel, which represents nothing less than 6% of the annual European consumption. Forecasts showed that if no actions were taken, the cost due to congestion would have reached approximately 1%

of the Community GDP in 2010.

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In this context, the balance between transport modes has been shifted at the very heart of a more global sustainable development strategy by the Göteborg European Council in 2001. The transport sector, suspected to be responsible of 50% of the European emissions of CO2 in 2010, cannot indeed stay apart from the global effort to reduce the emissions of green house gases. Unsurprisingly, road transport is the main culprit, since it is directly responsible of 84 % of the CO2 emissions due to transport. Railway transport is conversely creditworthy for less than 1% of transport sector’s air pollution, since it is mainly driven by electricity: while the Swedish high-speed trains X2000 emit 0.006 grams of CO2 per kilometer, passenger cars emit the same amount of carbon dioxide after 7 centimeters, and airplanes after 4 centimeters¹.

One of the major measures proposed is consequently the revitalization and the development of the railways, considered as the strategic domain on which the success of the efforts to limit the relative pre-eminence of the road transport will depend, particularly in the case of goods transport. An ambitious program aiming at developing a high-speed rail network throughout the European Union has been started the last decade with this intention (Figure 1.1). This effort is also meant to develop the freight capacity, by freeing up the lines that used to serve previously for passenger traffic.

Figure 1.1: High Speed Railways in Europe, 2009 (Source: Wikipedia, 2010)

1 http://www.banverket.se, May 2010

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So far, 9 of the 14 major infrastructure projects approved by the Essen European Council in 1994 have been achieved, or are in their construction phase. Some realizations are noticeable, such as the high-speed train line between Brussels and Marseille, and the Öresund Bridge linking Copenhagen and Malmö in Sweden.

The two remaining major projects are the completion of the alpines routes, such as the high-speed line Lyon - Torino, which will be needed within the next 10 years since the existing Alpine road tunnels (Fréjus tunnel and Mont Blanc tunnel) will soon reach their maximum capacity regarding safety; and the completion of an easier route through the Pyrenees between France and Spain (Figure 1.2).

Figure 1.2: Major railways projects waiting for completion (dotted lines) 2009 (Source:

Wikipedia, 2010)

Apart from these projects, new ones are considered by the European Commission of utmost importance: among them, the East-European high-speed line linking Paris to Vienna and the monumental bridge crossing the Fehmarn Belt between Germany and Denmark, a key link which will complete the North–South route connecting Central Europe and Scandinavia.

1.1.2 Trends in Sweden

In Sweden, railways capacity will have to be enhanced by 50% in order to meet the demand of the customers and to fulfill the environmental regulation by 2020 (Banverket, 2008). Hundreds of kilometers of railway track are already designed to allow train speed of 200 km/h (Figure 1.1). Most of these infrastructures are located along the routes Stockholm – Copenhagen, Stockholm – Göteborg and Göteborg – Malmö. There are plans to upgrade large sections of these lines to allow 250 km/h speeds, while some others railways are under construction: Trollhättan – Göteborg and the Bothnia line between Kramfors and Umeå in Norrland. The Bothnia line is already partly opened to traffic, and will be fully operational in autumn 2010.

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Besides these projects, the Swedish railway administration, Banverket, plans to build two high-speed lines between Stockholm and Malmö (Europe Line), and between Stockholm and Göteborg (Gothenland Line), which will allow speeds of 320 km/h (Figure 1.3). The Gothenland Line involves a corridor from Stockholm to Norrköping, Linköping and further away Jönköping, Borås and finally Göteborg. The Europe Line is a continuation of the Gothenland Line to the South from Jönköping to either Helsingborg, through a Helsingborg – Helsingør tunnel which has to be built, or to Malmö and Copenhagen via the Öresund Bridge.

The Gothenland Line is expected to be completed by 2025 or 2030, but optimistic forecasts predict that the sections between Göteborg and Borås, and between Södertälje and Linköping, could be opened to traffic by 2020. Concerning the Europe Line, since it may involve the construction of a tunnel under the Öresund, it is very likely to be opened after the Gothenland Line, i.e. after 2030 (Banverket, 2008).

Figure 1.3: High-speed lines projects in Sweden (Banverket, 2008)

1.1.3 Railway bridge stock in Europe and Sweden

A survey carried out in 2004 within the Sixth framework Programme of the European Commission (2002-2006) has taken inventory of all the existing railway bridges throughout 17 countries in Europe (Figure 1.4). It came out that 40.7% of the 219 718 built bridges are arches, 22.7% are made of concrete, 21.5% are steel bridges and 13.9%

are steel/concrete composite bridges, while 1.1% of them are not belonging to any

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category does not refer to a specific building material, but to a specific bridge layout.

In the survey, arch bridges with brick, stone and concrete barrels are assigned to the same category.

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Figure 1.4: Railway Bridge types in (a) Europe and (b) Sweden (Bell, 2004)

In Sweden, 79.3% of the 3620 listed bridges are concrete bridges, 13.8% are steel bridges, 4.1% are arch bridges, and only 1.4% are steel/concrete composite bridges (Figure 1.4b).

The survey shows clearly that the railway bridge stock in Sweden is very largely dominated by concrete bridge, followed by far by the steel bridges, the arch bridges and the steel/concrete composite bridges. It is interesting to note that this trend is radically different from the one in Europe, where arches are the most common type of bridges.

However, this relative pre-eminence of concrete bridges drops in the medium and long span ranges, as it is showed in Table 1.1. Meanwhile, the shares of steel bridges and composite bridges increase to 66.7% and 13.3% respectively.

Table 1.1: Railway bridges in Sweden – span profiles in percentage (Bell, 2004) Arch Concrete Steel Composite Total

< 10 m 5.7 85.9 8.4 0 100

10 – 40 m 1.2 72.6 23.1 3.1 100

> 40 m 6.7 13.3 66.7 13.3 100

This tendency is partly attributable to the properties of steel which allow lighter and more slender decks, and thus longer spans than concrete. Besides, high-speed railway steel bridges incorporate favorably a concrete slab to carry the tracks, to participate in the global and local strength of the composite structure, and to bring supplementary mass and dumping, which consequently decrease the noise when high-speed trains pass over the bridge. Furthermore, the extra mass brought by the concrete limits the

40,7%

22,7%

21,5%

13,9%

1,1%

Arch Concrete Steel Composite not specified

4,10%

79,3%

13,8%

1,4%

Arch Concrete Steel Composite 40,7%

22,7%

21,5%

13,9%

1,1%

Arch Concrete Steel Composite not specified

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dynamic phenomena, thus enhancing safety and comfort of the passengers (Petetin and Hoorpah, 2003).

In a cost reducing perspective, no expensive formwork to support the load from hardening concrete is needed when comparing steel/concrete composite bridges with concrete bridges, thanks to the good ability of the steel girders to carry the formwork.

Reduced construction time, and thus costs, compared to concrete bridges greatly contribute to the increasing popularity of composite bridges (Collin et al., 2008).

This popularity is illustrated by the growth of the use of composite bridges along the French high-speed railway network, one of the most developed in the world. The first high-speed South-East and Atlantic lines, built in the 1980s, have only pre-stressed concrete bridges, while the newer North line linking Paris to Lille include 15 steel and composite bridges, and 23 steel and composite bridges have been built along the Mediterranean line, opened to traffic in 2001. Based on the French experience in building high-speed railways, it is most likely that this trend will be confirmed along the planned Swedish high-speed network in the coming 20 years.

1.1.4 Infrastructures in a sustainable development perspective

Environmental awareness has strongly increased these last years, especially in the developed countries where societies have become increasingly preoccupied by the natural resource depletion, fossil fuel among others, and environmental degradation, such as the emission of green house gases. As a result, industries, businesses and public authorities are more and more assessing the way their processes impact the environment to provide “eco-friendly” products or services.

The building industry is of course affected by this global effort towards the minimization of the society’s impact on the environment: it is responsible of about 40%

of the total energy use in Sweden and needs approximately 7.5 billion tons of building material per year (Borg, 2001). To assess the order of magnitude of the air emissions due to the construction sector, it is noteworthy that producing 1 m³ of concrete corresponds approximately to a travel of 2000 km for one person by car or to about 3000 km by air, regarding the emission of carbon dioxide².

In the perspective of achieving a sustainable development, moving beyond compliance to environmental regulations, by implementing pollution prevention strategies or environmental management systems (EMS), has been found preferential by many institutions. Different methods have been developed with this intention (Life Cycle Assessment: Principles and Practice, 2006).

Seventeen of them have been identified in Bengtsson et al. (2000). These tools are well spread and known for most of them, but they have different characteristics. They strongly differ in their ambition and in their need of specific knowledge necessary to use them. The purpose of these methods ranges from a mapping of the environmental

2 COWI A/S, sustainable construction brochure

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issues of an organization, like a simple environmental inquiry, to an exhaustive analysis of the potential environmental impacts of a product during its entire lifetime.

This “cradle to grave” concept, called Life Cycle Assessment, is a methodological framework for evaluating and assessing the potential environmental impacts of a product, such as climate change, stratospheric ozone depletion, eutrophication, acidification, toxicological stress on human health and ecosystems, depletion of resources, water use, land use, noise, etc, over all four stages of a product or process life cycle: raw material acquisition, manufacturing, use/reuse/maintenance, and recycle/waste management.

The methodology originated in the late 1960s. Until the end of the 1980s, a large amount of studies was performed without a common theoretical framework.

Consequently, the results differed greatly, even if the objects of the studies were the same and thus preventing life cycle assessment from becoming a more widely accepted analytical tool (Udo de Haes, 1993). At the beginning of the 1990s, a broader interest for LCA emerged, primarily thanks to company’s need of environmental information to provide to clients, or governmental agencies. Consequently, the LCA methodology has been further developed, but in two directions: one towards an improvement of the existing method, and another one aiming at building up simplified, or streamlined, approaches for internal use or for screening purpose for future more complete studies (Weitz et al., 1996).

Meanwhile, a large effort towards the harmonization of the methodology has been carried out, through a wide exchange between LCA practitioners throughout the world and thanks to the work of the Society of Environmental Toxicology and Chemistry (SETAC). This led to the first attempt of LCA standards in the International Standards Organization (ISO) 14000 series in 1997, updated in 2002.

LCA has then been identified as a robust tool to support decision making in the construction sector, since a scientifically accepted and worldwide spread method has been established. However, some specific factors inherent to this sector, such as long service life, inhomogeneous lifetimes for different building materials included in the same system or the high potential for recycling and reuse of building materials, imply a specific implementation of the life cycle assessment methodology (Borg, 2001).

1.2 Aim and Scope of the study

This thesis aims at establishing a state of practice of Life Cycle Assessment: the past and latest developments regarding the methodology itself are investigated, from the conventional standardized method to the simplified approaches, which are increasingly used when quick and effective decisions must be made (Chapter 2).

Large panels of environmental assessment studies that used the LCA framework, which have been carried out to compare the environmental performances of transportation systems and to explore the burdens from railway transportation system and bridges, are gathered in an attempt to establish a state-of-the-art review of the use of LCA in the field of bridges and railway infrastructure systems (Chapter 3).

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A second objective of the thesis is to implement a simplified quantitative LCA that aims at comparing the environmental performance of two railway bridge designs, in order to provide environmental information to decision-makers when a decision is to be made regarding the bridge’s layout at an early stage in the design process (Chapter 4).

The tool is capable of assessing the life-cycle environmental burden of different railway bridge types, from reinforced concrete beam or trough bridges, to steel-concrete composite girder bridges. However, it is not suitable for the evaluation of the environmental effects of suspension bridges, cable-stayed bridges, or arch bridges.

It covers the entire life-cycle of bridges, from raw material extraction to final material disposal, for the substructure and the superstructure. Only the combustion of fossil fuels is considered, the extraction, processing and distribution are omitted. The production of electricity is not considered. Processes and materials found insignificant in the previous researches are omitted, such as formwork, ground preparation, bearings and expansion joints. Only the production of steel and concrete is included in the model. Various maintenance activities are modeled, like the replacement of the bearings or expansion joints, re-painting of the steelwork and replacement of the whole bridge deck. They sometimes require the complete closure of the bridge to train traffic, resulting in the shift of the passenger and freight transport to the road. Finally, different disposal scenarios are modeled for steel, namely direct recycling or landfilling, while reinforced concrete is sorted, then partly recycled and landfilled.

The simplified approach focuses on a limited set of material and emission flows.

Emissions to the air, namely carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nitrogen oxides (NOX), sulfur dioxide (SO2), non-methane volatile organic compounds (NMVOC) and particulate matter (PM10), and water (oils, biological oxygen demand, total suspended solid, dissolved organic compounds), and generated solid wastes are taken into account. Impacts to the environment are then assessed for 6 impact categories, namely climate change, abiotic resource depletion, acidification, eutrophication, photo-oxidant formation and human toxicity.

A comparative environmental assessment is carried out using the developed tool, aiming at comparing the environmental impacts of a ballasted and fixed track system installed on the Banafjäl Bridge, a high-speed steel-concrete composite railway bridge on the Bothnia Line in Sweden (Chapter 5). Only the superstructure of the bridge, with the exception of the bracings, is considered. The actual curvature of the bridge is disregarded. The maintenance and repair activities of the track systems are not accounted since no data regarding the associated environmental pressure has been found.

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Chapter 2 Review of the structure of the Life Cycle Assessment process

2.1 Life Cycle assessment

A Life Cycle Assessment is a so-called “cradle-to-grave” approach, which means that all majors’ activities during the life time of the studied product are accounted, from the extraction of raw materials, manufacture, use, and maintenance, to its final disposal or recycling.

The raw material acquisition phase includes all processes involved in the removal of raw materials from the earth, as well as the transport of these materials from the extraction site to the processing units. The manufacturing stage consists of the processes involved in the conversion of the raw materials into a material usable to fabricate finished product (such as concrete or steel), and the product manufacturing, packing and distribution. The use phase relates to the real use, reuse and maintenance of the product, until it is disposed or recycled. All the processes associated with product disposal management are accounted in the end-of-life stage.

2.2 Framework

Life Cycle Assessment (LCA) is a systematic and phased methodology (SAIC, 2006).

Its framework has been internationally standardized in the ISO 14040 series standards, even though new advances continue to be made. Originally, the Society of Environmental Toxicology and Chemistry (SETAC) differentiated five components in the methodology: goal definition, inventory, classification, valuation and improvement analysis (Guinée et al., 1993a). However, the ISO standards published in 1997 no longer considered the improvement analysis step as a stand-alone phase, but it was identified as having an influence throughout the whole LCA process. Another methodological component which interacts with all the others, namely life cycle interpretation, was introduced instead (Rebitzer et al., 2004).

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At the time being, four components are considered being part of the LCA methodology as illustrated in Figure 2.1: goal definition and scoping, inventory analysis, impact assessment and interpretation (Rebitzer et al., 2004; SAIC, 2006).

Figure 2.1: Phases of an LCA (Source: ISO, 1997)

The goal and scope definition provides the goal of the assessment. It describes the product system and the context in which the assessment is to be made, and limit the scope of the study by setting up its boundaries (SAIC, 2006). The inventory analysis estimates the consumption of inputs, such as energy, water and natural resources, and the releases to the environment, like air emissions, solid waste generation, waste water discharges, attributable to a product’s life cycle. The impact assessment provides the basis for assessing the potential environmental burden of the materials usage and emissions identified in the inventory analysis, regarding a number of potential impact categories. Finally, interpretation occurs at every stage in an LCA: conclusions can be drawn directly from the inventory analysis results, while interpretation based on the impact assessment results is preferable when trade-offs are to be made (Rebitzer et al., 2004).

2.3 Goal and Scope definition

The goal and scope definition phase provides the type of information needed to inform the decision-makers, the accuracy of the results and the way they should be interpreted and presented to be usable. The decisions made at this step influence the choices to be made within the other phases of the LCA, by specifying the necessary time and resources, or by impacting how the analysis is conducted (SAIC, 2006), and are therefore decisive for the results of the assessment (Rebitzer et al., 2004).

The goal of the assessment must be unambiguously and transparently defined, for instance choosing the alternative with the least impact on the environment or guiding

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the development of a new product or process towards the minimization of its environmental effects, as well as the reasons for carrying out the study (Guinée et al, 2001). Two distinct categories of LCA goals exist: an LCA can be performed from an attributional or a consequential point of view (Finnveden et al., 2009). The first point of view implies that the assessment aims at describing the system and its environmental exchanges, while the second point of view deals with the assessment of the way “the environmental exchanges of the system can be expected to change as a result of actions taken in the system” (Rebitzer et al., 2004).

The study parameters, i.e. the natural resources or emissions considered in the assessment, are determined with regard to the type of information needed to inform the decision-makers (SAIC, 2006). For example, if the study aims at choosing among a number of alternatives the bridge that contributes the least to the climate change, the analysis will pay a particular attention to the emissions of greenhouse gas.

The goal and scope definition step provides also the time scale and the level of specificity of the study, i.e. the spatial scale, ranging from a generic study to a product- specific assessment, in order to determine the type of data that has to be collected (SAIC, 2006). The accuracy of the data depends on the intended audience, either internal decision-makers or a public forum, and on the criticality of the decisions to be made based on the assessment’s results (Wenzel, 1998).

The way the results are displayed is defined through a functional unit, which is a quantitative description of the needs fulfilled by the product or process being analyzed (Rebitzer et al., 2004). When two products or services are compared, the basis for comparison should reflect an equivalent service provided to the customer: in the case of a bridge, an adequate functional unit could be “enable 5000 vehicles a day to go from a point A to a point B over 100 years”. It is noticeable that to perform an attributional assessment, the magnitude of the functional unit is of little importance since the system is linearly modeled. However, the functional unit’s magnitude should reflect that of the changes investigated for a consequential analysis, since the consequences are not linked linearly to the changes (Rebitzer et al., 2004).

Depending on the goal of the study, the desired accuracy of the results and the available time and resources, the scope of the study is defined by determining the life- cycle stages and the processes to be included in the analysis. Weidema (1998) argued that the scope of an LCA is also determined by “the area of validity of the decision with respect to time, space, and interest groups affected”.

2.4 Life Cycle Inventory

2.4.1 Process models

SAIC (2006) reported four major steps in a Life Cycle Inventory (LCI). At the first step, a process flow chart is constructed, in which the inputs and outputs of each process or system are mapped, according to the system boundaries established at the goal and scope definition step. All energy and material flows, and the chosen emissions to the air, water and soils are accounted. In addition to that, the transportation from

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one process location to another is included in each subsystem. Rebitzer et al. (2004) identified the processes to be included in the product system as those that are suspected to contribute significantly to the product’s function. They also described the possible strategies to set the boundaries between the studied system and the others, for instance how to handle the processes that provide more than one product, which refers to the allocation procedure in the literature. A recurrent allocation problem occurs for instance when dealing with recycled or re-used materials: how to account for the environmental benefit associated with recycling? Should recycled or re-used materials contribute negatively to the Life Cycle Inventory for example? The answers to these questions must be stated at the goal and scope definition step.

The second step aims at developing a data collection plan, in order to make sure that the data’s quality meets the requirements described in the goal and scope definition stage, when selecting the data sources to perform the LCI. Inventory data can be obtained from various sources (Brattebø et al., 2009; SAIC, 2006), such as companies, suppliers and producers, governments, journals and articles, reference book, earlier LCA studies, specific computer based databases, or best engineering judgment. Based on Rebitzer et al. (2004), Finnveden et al., 2009 and on further personal researches, Table 2.1 presents various inventory data sources for a number of processes and materials used in the building sector. A more extensive summary of LCI data resources in the world can be found in Curran and Notten (2006).

Table 2.1: Indicative, non-exhaustive list of LCI databases

Database name Scope Managed by Further information

Environmental profile report for the European aluminum

industry

Aluminum production and transformation

processes

European aluminum

association http://www.aluminium.org

Eco-profiles of the European

plastics industry Plastics products

production PlasticsEurope http://www.plasticseurope.org

Life Cycle Inventory of Portland Cement Concrete

Production of ready mixed, masonry, and

precast concrete.

Portland cement

association http://www.cement.org

Worldsteel Life Cycle Inventory Steel products

IISI (International Iron and Steel

Institute) http://www.worldsteel.org

Life cycle assessment of nickel

products Nickel products Nickel institute http://www.nickelinstitute.org

European Reference Life Cycle Database (ELCD)

Energy, material production, systems, transport, end-of-life

treatment

European Commission http://lct.jrc.ec.europa.eu

US NREL database Global US National

Renewable Energy

Laboratory (NREL) http://www.nrel.gov/lci/

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Table 2.1: (continued)

Database name Scope Managed by Further information

JEMAI database Global

Japan Environmental

Management Association for Industry (JEMAI)

http://www.jemai.or.jp/english

ProBas database

Energy, materials and products, transport, waste

management

German federal environmental

agency (Umweltbundesamt)

http://www.probas.umweltbundesamt.de

SPINE@CPM database Global Chalmers CPM,

Göteborg, Sweden http://www.cpm.chalmers.se

Ecoinvent

Energy supply, resource extraction,

material supply, chemicals, metals, agriculture, waste

management services, and transport services.

The Ecoinvent

Centre, Switzerland http://www.ecoinvent.ch

ETH-ESU 96 Database

Energy: Electricity generation and related processes like

transport, processing, waste

treatment

ETH Zurich, Switzerland

BUWAL 250

Packaging materials (plastic, carton, paper, glass, tin

plated steel, aluminum), energy,

transport, waste treatments

Swiss Federal Office for the Environment

(FOEN)

IDEMAT 2001

engineering materials (metals,

alloys, plastics, wood), energy and

transport

Delft Technical University, The Netherlands

European Database for Corrugated Board - Life Cycle

Studies

Corrugated board (packaging)

production

FEFCO (European Federation of Corrugated Board

Manufacturers)

http://www.fefco.org

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Many of these databases offer aggregated data, i.e. composite resource consumptions, wastes, and emissions per kilogram of material produced, while the Ecoinvent and the US NREL databases for instance provide disaggregated data for each process. On one hand, the aggregated industry data, readily available, are useful to model the production of globally traded products, such as aluminum or steel, since the LCA practitioner does not necessarily know the origin of the material he is dealing with.

However, some argue that this data lack of transparency and might be biased. On the other hand, disaggregated data offer the opportunity to adapt the data to the actual processes and technologies used in the production of the studied materials (Finnveden et al., 2009).

The data are gathered at the third step. The data collection and compilation is often the most work- and time-consuming steps in an LCA (Rebitzer et al., 2004). When a rapid decision-making process is required, simplified, or streamlined, approaches have to be employed. A number of these methods focus their efforts on saving time at the Life Cycle Inventory step, where the time saving potential is maximal. The simplifying strategy to be used depends on the goal and scope of the study, the required level of detail, the acceptable level of uncertainty and the available resources (Rebitzer et al., 2004). The approaches of LCA simplification are further presented and discussed in a specific section of this report.

The fourth and last step of a LCI provides an evaluation and a documentation of the inventory results. Depending on the goal of the study, they can be formatted in different ways to put in perspective the information: the relative contribution of the life-cycle stages or the components of the system can be clarified, in terms of energy consumption, resource use or releases to the environment (SAIC, 2006).

2.4.2 Other approaches for LCI

An alternative to the Life Cycle Inventory (LCI) based on process modeling has been developed, the economic input-output modeling, referred in the literature as I/O-LCA.

Its framework has been established in the first half of the 20th century by Wassily Leontief, who received the Nobel Prize in 1973. The studied system is modeled using economic flow databases, which are supplied by the statistical agencies of national governments (Finnveden et al., 2009). The entire economy is divided into distinct sectors, and represented in a matrix, where each sector is represented by one row and one column. The matrix financially describes the exchanges from one sector to another.

The environmental outputs are then calculated “by multiplying the economic output at each stage by the environmental impact per dollar of output” (SAIC, 2006).

The I/O model offers broader system boundaries, but a low level of details. It is thus applicable for system comparison on a regional, national, or international level, while comparisons within one industrial sector cannot be performed. Up-to-date databases are available, such as the EIO-LCA database provided by Carnegie Mellon University³

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in the US or the on-line tool provided by Statistiska centralbyrån in Sweden⁴. Other databases are referenced in Finnveden et al. (2009).

Hybrid models, which combine the I/O model with process models, have also been proposed to implement the advantages offered by both approaches, by for example analyzing the main processes in detail using process models, while estimating associated far upstream flows using I/O model (tiered hybrid method). MIET, for Missing Inventory Estimation Tool, is a publicly available spreadsheet to perform LCA based on this method. Another method, referred to as input-output based hybrid method, is based on disaggregated input-output matrix to improve the resolution of the I/O model. A third method, the so-called integrated hybrid method, for which both the process-based model and the input output-based model are merged into one matrix, has been proposed (Rebitzer et al., 2004).

2.5 Life Cycle Impact Assessment

The Life Cycle Impact Assessment (LCIA) phase of an LCA evaluates the potential impacts on the environment of the resource use and releases identified during the Life Cycle Inventory stage, regarding a set of impact categories. Even though conclusions can be drawn from the LCI results, an impact assessment has to be performed when trade-offs are to be made.

Numerous Life Cycle Impact Assessment methods have been developed and implemented in most computer based LCA tools. For instance, fifteen methods have been included in the Ecoinvent database, namely:

- CML 2001;

- Cumulative Energy Demand (CED);

- Cumulative Exergy Demand (CExD);

- Eco-indicator’99;

- Ecosystem Damage Potential (EDP);

- Ecological Footprint;

- the method of ecological scarcity (UBP’97);

- Ecological Scarcity Method 2006;

- Environmental Design of Industrial Products 97 (EDIP’97);

- EDIP 2003;

- Environmental Priority Strategy 2000 (EPS 2000);

- IMPACT 2002+;

- IPCC 2001 and 2007 (Climate change);

- TRACI.

These methods differ, among other, in the investigated LCI data, the sets of impact or damage category used, or the type of model chosen to characterize the impacts or damages to the environment (midpoint or endpoint models). For instance, CED and CExD aim only at investigating the energy use throughout the life cycle of a product.

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However, the main methodological elements are rather similar for all methods. A complete description of these LCIA methods can be found in Hischier et al. (2009), with all references to the specific literature for each of them.

Pennington et al. (2004) identified three mandatory and three optional steps to conduct an LCIA. To illustrate these steps, examples from the CML 01 method, described in Guinée et al. (2001), are given.

2.5.1 Selection of the impact categories

The first step consists in selecting the impact categories and the indicator for impact category, which are relevant for the study. This step is performed in relation with the goal of the study, stated at the goal and scope definition phase (SAIC, 2006). The LCIA standards, ISO 14042, identified three groups of impact categories, referred in the literature as AoPs, for Areas of Protection (Pennington et al., 2004): resource use, human health and ecological consequences. Guinée et al. (2001) distinguished three sets of impact categories, depending on environmental relevance (Table 2.2). The first group, “Baseline impact categories”, includes the impact categories which are included in the majority of the LCA studies. The second group, “Study-specific impact categories”, comprises categories that may be included if it is required by the goal of the study, and if data are available. The third group, “Other impact categories”, includes the other categories which require further research to be used in LCA studies.

Table 2.2: Sets of impact categories (Guinée et al., 2001)

Group A

Baseline impact categories Group B

Study-specific impact categories Group C Other impact categories

Depletion of abiotic resource Land use – loss of life support

fonction Depletion of biotic resources Land use – land competition Land use – loss biodiversity Desiccation

Climate change Freshwater sediment ecotoxicity Malodorous water Stratospheric ozone

depletion Marine sediment ecotoxicity Etc.

Human toxicity Ionizing radiation Freshwater aquatic

ecotoxicity Malodorous air Marine aquatic ecotoxicity Noise

Terrestrial ecotoxicity Waste heat Photo-oxidant formation Casualties

Acidification Eutrophication

Abiotic, or non-living, resources are natural resources, such as crude oil, natural gas or iron ore. Land use refers to the consequences of human land use, like the depletion of land as a resource, or the impact of land use on biodiversity and life support functions.

Climate change relates to the heat radiation absorption of the atmosphere, while stratospheric ozone depletion refers to the thinning of the stratospheric ozone layer.

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Human toxicity and eco-toxicity categories cover the impact of toxic substances on human health, and aquatic, terrestrial and sediment ecosystem respectively. Photo- oxidants, such as ozone, are formed in the troposphere by the action of sunlight on a variety of air pollutants. They impact human health and the ecosystems.

Eutrophication refers to the excessive level of nutrients in both aquatic and terrestrial ecosystems, which can lead to an elevation of the biomass production, and change surface water to unfit water for drinking.

2.5.2 Classification

The second step referred to in the literature as the classification, assigns the inventory data to the chosen impact categories (Pennington et al., 2004). If a LCI item contributes to several impact categories, it can be assigned either by dividing it to the impact categories when the effects depends on each other, or by assigning the all item to all impact categories when the effects are independent (SAIC, 2006). Table 2.3 presents examples of LCI data classification for commonly used impact categories, with the associated indicators.

Table 2.3: Commonly used impact categories (SAIC, 2006)

impact category Scale Examples of LCI data Indicator Depletion of abiotic

resource Global Quantity of minerals used

Quantity of fossil fuels used ADP (Abiotic Depletion Potential)

Climate change Global Carbon Dioxide (CO2) Nitrogen Dioxide (NO2) Methane (CH4)

GWP (Global Warming potential)

Acidification Regional, local

Sulfur Oxides (SOX) Nitrogen Oxides (NOX) Ammonia (NH4)

AP (Acidification Potential)

Eutrophication Local

Phosphate (PO4) Nitrogen Oxide (NO) Nitrogen Dioxide (NO2) Nitrates

Ammonia (NH4)

EP (Eutrophication Potential)

Photo-oxidant

formation Local Non-methane hydrocarbon

(NMHC) POCP (Photo-Oxidant

Creation Potential)

Stratospheric Ozone

Depletion Global Chlorofluorocarbons (CFCs) Hydrochlorofluorocarbons (HCFCs)

ODP (Ozone Depletion Potential)

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2.5.3 Characterization

The third step, the characterization, calculates the impact category indicators by using generic so-called characterization factors. Those factors are obtained from characterization models, and are available in the literature (Guinée et al., 2001) or in the form of databases in computer based LCA tools (Pennington et al., 2004).

Equations (2.1) and (2.2) describe how indicators for each impact category are calculated from the inventory data (Brattebø et al., 2009).

(2.1)

(2.2)

Where eij is the emission of the LCI item j for total consumption of input parameter i;

xi is the consumption of the input parameter i; fij is the emission of LCI item j per unit input parameter i; dk is the total potential impacts in impact category k, expressed in equivalents (Table 2.4), and cjk is the characterization factor for LCI item j to impact category k.

Table 2.4: Unit of commonly used category indicators (Guinée et al., 2001)

Impact Category Category indicator Unit

Depletion of abiotic resource

ADP (Abiotic Depletion Potential)

kg antimony equivalent/kg extracted (kg Sb eq./kg)

Land use One for all types of land use

(dimensionless) m².year

Climate change GWP (Global Warming

Potential) kg carbon dioxide equivalent/kg emitted (kg CO2 eq./kg)

Human toxicity HTP (Human Toxicity Potential)

kg 1,4-dichlorobenzene equivalent/kg emitted

(kg 1,4 DCB eq./kg)

Acidification AP (Acidification Potential)

kg sulfur dioxide equivalent/kg emitted (kg SO2 eq./kg)

Eutrophication EP (Eutrophication

Potential) kg phosphate equivalent/kg emitted (kg PO43- eq./kg)

Photo-oxidant

formation POCP (Photo-Oxidant

Creation Potential) kg ethylene equivalent/kg emitted (kg C2H4 eq./kg)

Stratospheric Ozone

Depletion ODP (Ozone Depletion

Potential) kg CFC-11 eq./kg

Design of railway bridges considering LCA

Design of railway bridges considering LCA

VINCENT THIEBAULT

Master of Science Thesis

Stockholm, Sweden 2010

Design of railway bridges considering LCA

Vincent Thiebault

Preface

Abstract

Résumé

Contents

Chapter 1 Introduction

1.1 Background

1.2 Aim and Scope of the study

Chapter 2

Review of the structure of the Life Cycle Assessment process

2.1 Life Cycle assessment

2.2 Framework

2.3 Goal and Scope definition

2.4 Life Cycle Inventory

2.5 Life Cycle Impact Assessment